Recently, many composite semi-permeable membranes, in which a skin layer including polyamides obtained by interfacial polymerization of polyfunctional aromatic amines and polyfunctional aromatic acid halides is formed on a porous support, have been proposed (Patent documents 1 to 4). A composite semi-permeable membrane, in which a skin layer including a polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional alicyclic acid halide is formed on a porous support, has also been proposed (Patent document 5).
The porous supports include, for example, those in which a microporous layer having a substantial separation function is formed on a surface of a substrate. The substrate includes, for example, a woven fabric, a nonwoven fabric, a mesh net and a foaming sintered sheet, made of materials such as polyester, polypropylene, polyethylene, polyamide and the like. In addition, materials for forming the microporous layer include various materials, for example, such as polyaryl ether sulfones (e.g. polysulfones, polyether sulfones), polyimides and polyvinylidene fluorides, and particularly from the viewpoint of chemical, mechanical and thermal stability, polysulfones and polyaryl ether sulfones have been preferably used.
As for these composite semi-permeable membranes, chemical resistance that can endure various oxidants, particularly chlorine washing, has been required as a result of pursuit of low cost due to more stable operability and simple usability as well as prolongation of membrane lifetime, in various water treatments including desalination plants.
The composite semi-permeable membrane has a practical chemical resistance, but it may not be said that such a membrane has chemical resistance to endure against routine or intermittent chlorine sterilization. Therefore, development of a composite semi-permeable membrane having higher chemical resistance as well as a practical level of water permeability and salt-blocking property, particularly development of a porous support exhibiting an excellent chemical resistance, has been desired.
On the other hand, a porous cured epoxy resin that is a separation medium capable of selectively distinguishing a substance having a plane molecular structure, such as dioxin or PCB (polychlorinated biphenyl), and capable of having a low back pressure, as well as able being processed on a large scale, has been developed (Patent document 6). The porous cured epoxy resin is a non-particle aggregation type porous object including a columnar three-dimensional branched structure, wherein the porous object has a porosity of 20 to 80% and an average pore diameter of 0.5 to 50 μm.